Fix lowering and function detection + add test

Author: gbaraldi

src/llvm-pass-helpers.cpp

@@ -88,7 +88,7 @@ llvm::CallInst *JuliaPassContext::getPGCstack(llvm::Function &F) const
     return nullptr;
 }
 
-llvm::CallInst *JuliaPassContext::getOrAddPGCstack(llvm::Function &F) const
+llvm::CallInst *JuliaPassContext::getOrAddPGCstack(llvm::Function &F)
 {
     if (pgcstack_getter || adoptthread_func)
         for (auto &I : F.getEntryBlock()) {
@@ -101,8 +101,11 @@ llvm::CallInst *JuliaPassContext::getOrAddPGCstack(llvm::Function &F) const
             }
         }
     IRBuilder<> builder(&F.getEntryBlock().front());
+    if (pgcstack_getter)
+        return builder.CreateCall(pgcstack_getter);
     auto FT = FunctionType::get(PointerType::get(F.getContext(), 0), false);
     auto F2 = Function::Create(FT, Function::ExternalLinkage, "julia.get_pgcstack", F.getParent());
+    pgcstack_getter = F2;
     return builder.CreateCall( F2);
 }
 

src/llvm-pass-helpers.h

@@ -90,7 +90,7 @@ struct JuliaPassContext {
     // Gets a call to the `julia.get_pgcstack' intrinsic in the entry
     // point of the given function, if there exists such a call.
     // Otherwise, creates a new call to the intrinsic
-    llvm::CallInst *getOrAddPGCstack(llvm::Function &F) const;
+    llvm::CallInst *getOrAddPGCstack(llvm::Function &F);
     // Gets the intrinsic or well-known function that conforms to
     // the given description if it exists in the module. If not,
     // `nullptr` is returned.

test/ccall.jl

@@ -1966,3 +1966,14 @@ let llvm = sprint(code_llvm, world_counter, ())
     # the world age should be -1 in generated functions (or other pure contexts)
     @test (generated_world_counter() == reinterpret(UInt, -1))
 end
+
+function gc_safe_ccall()
+    @ccall gc_safe=true jl_get_cpu_features()::String
+end
+
+let llvm = sprint(code_llvm, gc_safe_ccall, ())
+    # check that the call works
+    @test gc_safe_ccall() isa String
+    # check for the gc_safe store
+    @test occursin("store atomic i8 2", llvm)
+end